Season Six, also known as Day 6, of the television series 24 premiered in the United States on Sunday, January 14, 2007, the UK on January 21, 2007 and in Australia on January 30, 2007. The season's storyline began and ended at 6:00 a.m. It is set 20 months after the events of the fifth season.

Season Six is set 20 months after Season Five. Over the last 11 weeks before Day 6, the United States has been targeted coast-to-coast in a series of suicide bombings. A man named Abu Fayed agrees to give the U.S. the location of Hamri Al-Assad, the supposed terrorist mastermind of these attacks, in exchange for former CTU Agent Jack Bauer with whom he has a personal grudge. As a result, President Wayne Palmer has negotiated the release of Bauer, who was illegally captured by Chinese government agents, under "high-price" terms.

Season 6 can be divided into three main acts with the first two overlapping somewhat:

Terrorist attacks claim thousands of American lives. Jack struggles to convince authorities that Abu Fayed is responsible and also discovers that his own family is involved.

With Fayed in possession of five suitcase nukes, CTU races to find them to prevent another disaster from taking place.

After the nukes are recovered, the Chinese manipulate Jack into giving them one of the circuit boards, elevating tensions between the United States and Russia.

Agent Jack Bauer, having been taken prisoner by China 20 months earlier, is released under a deal arranged by President Wayne Palmer. Jack is immediately asked to sacrifice himself to Abu Fayed, who has offered CTU Hamri Al-Assad, who is believed to be the terrorist mastermind behind the suicide bombings of the last 11 weeks. Jack finds out, however, that Assad is actually trying to stop the attacks, which were orchestrated by Fayed. He escapes and saves Assad which requires him to kill Curtis Manning who is bent on revenge. Having found out that Fayed is planning to detonate five suitcase nuclear bombs, CTU agents attempt to retrieve one of them but they are too late. While crying over the loss of his friend, Jack watches in horror as a nuclear blast destroys Valencia.

Jack discovers that his father Phillip and brother Graem are working against CTU and have been for some time. This reunites Jack with his nephew Josh Bauer and sister-in-law Marilyn Bauer who tells him that Audrey Raines is dead. Morris O'Brian is lured out of CTU, captured by Fayed and forced to arm the remaining nuclear bombs. After defusing one of them, Jack enlists the help of former President Charles Logan. Logan claims that his connection with the Russian Consulate General, Anatoly Markov can help Jack find Dmitri Gredenko, a general planning to arm RQ-2 Aerial Drones with the bombs to attack the U.S. Dissatisfied with Wayne Palmer's leadership during the crisis, Reed Pollock and a co-conspirator named Carson plan to assassinate Palmer and frame Al-Assad for it. Before Tom Lennox can prevent the attack, their bomb explodes, killing Assad and leaving Palmer in critical condition.

Vice President Noah Daniels assumes executive powers and threatens retaliation. Logan fails to blackmail Markov into giving up Gredenko, so Jack breaks into the Russian Consulate and tortures information out of him. President Logan convinces his ex-wife Martha to call the Russian First Lady, Anya Suvarov. As a result, Yuri Suvarov authorizes action against the consulate by a CTU team (led by new Director of Field Operations Mike Doyle). Jack immediately gives CTU Gredenko's location, but it is too late, as Gredenko has already launched a drone toward San Francisco. Jack manages to locate the drone's pilot and crash land the drone but radiation is released during the crash. Noah Daniels authorizes a nuclear strike against the Middle-East but Wayne Palmer is brought out of his coma to intervene.

Gredenko is captured by CTU and he agrees to help bring in Fayed in exchange for amnesty, but warns Fayed instead. Gredenko dies and Jack manages to track down Fayed. After a struggle, Jack single-handedly kills Fayed and finds the two remaining bombs. Jack then receives a phone call from Audrey, who is apparently still alive and is then turned over to Cheng Zhi. Cheng demands a Russian circuit board from one of the nukes, information that could start a war, in exchange for Audrey's freedom. President Palmer reluctantly authorizes Jack's plan but collapses during a press conference, allowing Daniels to assume executive duties and reverse the order. Jack goes rogue and goes through with the exchange, learning that Audrey has endured pharmaceutical torture. His plan to destroy the board fails and Cheng gets hold of it.

Russia discovers that the Chinese have the circuit board and threatens military action. Cheng discovers that the board has been damaged and calls Phillip Bauer to fix it. Jack gets a lead from Audrey about Cheng's location but before they can use it, CTU is infiltrated by Chinese mercenaries, led by Zhou, and most members of CTU are taken hostage. Milo is fatally shot when he steps up to protect Nadia. Jack Bauer, Mike Doyle and others are able to kill the mercenaries and they learn that one of Phillip Bauer's conditions for helping the Chinese was that his grandson Josh be delivered to him. Phillip Bauer calls the White House and offers to give the circuit board for Josh, and they agree. Doyle takes Josh from Jack to go ahead with the exchange.

Jack finds out about the deal and gets help from Bill Buchanan who is working against the government. The exchange fails as Jack predicted and Phillip Bauer manages to capture Josh on an offshore oil rig while still in possession of the circuit board. Daniels decides to launch an air strike against the oil rig but Jack and Bill commandeer a helicopter in order to save Josh. They arrive in time to kill Cheng's men, capture Cheng alive and rescue Josh. Phillip Bauer dies in the subsequent airstrike. Jack confronts Audrey's father by whom he feels abandoned and lashes out. Heller apologizes but convinces Jack that Audrey would be safer without him. Jack tells a sleeping Audrey that even though he loves her, he must let her go for her own sake. He walks outside to a cliff and stares off at the ocean at an uncertain future.

A shocking twist from the fourth episode was the detonation of a suitcase nuke that killed twelve thousand civilians. The subsequent episodes, however, hardly showed any of the panic that would result from this. David Fury explained the development by saying that the intended writing direction kept fluctuating. "In the early seasons of 24, [the writers tried] to map out stories and arc out stories [beforehand] a little bit more than they did, say, in seasons four and five, and four and five turned out to be two of most successful seasons."[3] The nuclear threat was defused before the end of the season, leading to a story that was more personal for Jack. A panel of writers at Comic-Con said that they originally planned for Tony Almeida to return in the sixth season finale.[4]

A ten minute prequel to the sixth season of 24 is available on the Region-1 version of the Season 5DVD. The clip begins seven months after Day 5 and shows the Chinese torturing Jack trying to learn the identity of a double agent in their ranks. What appear to be American covert-ops soldiers break into the complex and free Jack, bringing him to a Chinese man named Hong Wai. As Jack flinches in recognition of Hong, the Chinese show up and thank Jack for identifying the double agent they had suspected all along. Cheng Zhi then executes Hong.

Additionally, an epilogue to Season 6 was released called 24: Debrief. It was first made available to American Express cardholders but was later released on the Season 6 DVD.

The original trailer for the sixth season opens with Kiefer Sutherland breaking the fourth wall and thanking the fans. The trailer features scenes from the first four episodes and sets Jack Bauer up to be sacrificed. It was released on October 24, 2006.

Eddie Izzard was cast as Darren McCarthy but left the show after one day of filming. According to Izzard, producers wanted to option further dates, but he was unavailable due to working on The Riches.[5] He was replaced by David Hunt.

Some members of the production staff cite Season 6 as their most disappointing season. In a 2010 interview, Howard Gordon said "I feel as though the story made a very wrong turn in season 6".[6] Also, when speaking about Season 7, Kiefer Sutherland said "We hit a couple rough spots with a lot of our viewers in Season 6, and we really wanted to remedy that".[7] Nevertheless, the season received many positive reviews, and holds a Metacritic score of 79 out of 100.[8] For this season, Jean Smart received the Emmy nomination for Outstanding Guest Actress in a Drama Series and Kiefer Sutherland received his sixth nomination for Outstanding Lead Actor in a Drama Series.

Twenty months after Jack Bauer's (Kiefer Sutherland) capture by the Chinese, terrorist attacks rock America. Jack returns in a deal made by President Wayne Palmer (DB Woodside). Jack is handed over to Abu Fayed (Adoni Maropis), who will in turn give the location of the man responsible for the attacks: Hamri Al-Assad (Alexander Siddig). Meanwhile, Karen Hayes (Jayne Atkinson) and Tom Lennox (Peter MacNicol) argue whether or not to suspend the rights of Muslim Americans.

Jack finds out that Fayed, not Al-Assad, is behind the attacks, and manages to escape. Jack teams up with Al-Assad to stop a suicide bomber on a subway. FBI agents search the Islamic-American Alliance offices in D.C. under dubious pretenses, to the chagrin of Sandra Palmer (Regina King). Ahmed Amar (Kal Penn) implements Fayed's plan in the suburbs.

Jack and Al-Assad track one of Fayed's men. Amar orders his classmate's father to deliver a package to Fayed. CTU discovers a wiring schematic for a nuclear device on a terrorist's laptop and learns of an elaborate plan to free a terrorist weapons programmer from the Palmdale Military Facility.

The terrorist programmer receives the device to re-configure the trigger. Sandra makes calls to her brother on behalf of Muslim boyfriend Walid Al-Rezani (Harry Lennix) to free him but he needs to stay since he suspects that certain people there are behind the attacks. President Palmer on the other hand pardons all past crimes of Assad in return of his continuing efforts to help the case. Curtis finds out and because of his history with Assad, confronts him to kill him. Jack must make a difficult choice between his prisoner and his partner. He is left with no choice and has to kill Curtis. CTU men race to find Fayed before he is able to detonate a suitcase nuke. while Wayne faces the toughest hour of his presidency, as a nuclear device detonates in Valencia.

Through Al-Assad's intel, Jack learns of a connection between his father Phillip Bauer (James Cromwell) and the nuke supplier. Jack contacts his brother, Graem (Paul McCrane), and demands information. As Fayed searches for triggers for his nukes, Al-Rezani spies on suspicious detention camp inmates.

Graem reveals a connection between his company and Darren McCarthy (David Hunt), who brokered the nukes to Fayed. Graem's motives are made clearer when he and Jack find their father. Security measures put in place by Lennox put pressure on the Arab members of CTU. Karen is blackmailed into resigning.

Jack and Phillip head to Graem's house to interrogate him. Graem reveals his involvement in the assassination of David Palmer. Wayne refuses Lennox's controversial plans to deny freedoms to Muslim-Americans. McCarthy kidnaps Morris O'Brian (Carlo Rota) and demands he arm the suitcase nukes.

Jack learns that Graem died as a result of his interrogation. Morris is brought to Fayed. Jack rescues Morris, but not before he is forced into programming the trigger. Fayed escapes with three suitcase nukes, which he is now capable of detonating. Lennox contemplates resigning, when Reed Pollock (Chad Lowe) brings an offer to the table.

Morris is brought back to CTU with Jack. Fayed contacts Dmitri Gredenko (Rade Serbedzija), a Cold War General, who is in L.A. and has been planning the day's events. Al-Assad begins work on a statement to address his people in Washington, D.C. Marilyn Bauer (Rena Sofer) is coerced into leading Jack into a trap by Phillip, who has taken Josh Bauer (Evan Ellingson) hostage.

Jack and Marilyn use one of Phillip's men to find out where he and Josh are. Returning to work puts unwanted pressure on Morris, especially after he hears of Milo Pressman's (Eric Balfour) heroism in saving Marilyn. Wayne prepares Assad's speech, unaware of conspiracy brewing within his own cabinet, and Jack is forced to turn to an unlikely source for help.

Jack meets with Charles Logan (Gregory Itzin) to gain information about the whereabouts of Gredenko, who continues with preparations to set off the remaining nukes. Tensions within the White House Bunker come to a boil just as Wayne and Al-Assad are about to address the nation, and CTU deals with the fallout from one of their employee's experiences earlier in the day.

Vice President Noah Daniels (Powers Boothe) assumes presidential duties from the wounded Wayne. Tom Lennox turns Reed Pollock in for attempting to assassinate Wayne. Jack, with the help of Logan, extracts Gredenko's plot from Anatoly Markov, but is unable to pass it to CTU.

Jack escapes the Russian consulate with the help of CTU led by the new head of field ops: Mike Doyle (Ricky Schroder). Logan and Martha Logan (Jean Smart) are reunited, which ends in tragedy. Daniels puts pressure on Lennox to frame Al-Assad for the attempt on Wayne's life.

Jack learns that Audrey Raines (Kim Raver) followed him to China and is now dead. Gredenko and Fayed launch the first nuclear drone. Even though CTU successfully subverts the bomb's detonation, Daniels goes forth with a nuclear retaliatory strike.

Jack, through CTU intel, finds and captures Gredenko, who negotiates a deal with CTU. To thwart the Daniels's plans to bomb Fayed's country, Karen and Sandra awaken Wayne from his chemically induced coma in hopes that he will rescind the order to strike before the missile launches.

Upon invoking the 25th Amendment, Daniels shows he is not above perjuring himself in order to obtain the presidency. Gredenko reluctantly helps CTU capture Fayed. Wayne resorts to risky medical treatments to maintain consciousness.

Wayne collapses at a press conference, making Daniels acting president. Against the orders of Daniels, Jack ditches his partner Doyle and proceeds alone to negotiate the release of Raines, who is being held captive by Cheng Zhi (Tzi Ma).

Daniels and his assistant Lisa Miller (Kari Matchett) engage in a seemingly-consensual, oval-office romance. Karen is forced to choose between her job and Bill Buchanan's (James Morrison). Cheng obtains the circuit board and escapes from both CTU and Jack. While being arrested by CTU, Jack realizes that Audrey, though free, was not returned unharmed.

The Russians learn too quickly that the Chinese have the circuit board, leading Daniels to suspect a spy. After some investigation, Daniels and Lennox plot to pass misinformation to the Russians through this unsuspecting informant. Nadia Yassir (Marisol Nichols) struggles with her newfound leadership at CTU when Division and Jack argue on how to handle the traumatized Audrey. Cheng discovers the circuit board is damaged.

Lisa complies with Daniels's plan to pass false intel through the Russian informant. CTU sends all their field agents to locate Cheng, not knowing that Cheng has already dispatched Chinese mercenaries to attack CTU Los Angeles.

Jack pursues Cheng, who has kidnapped Josh. Meanwhile, CTU recovers from the assault, but in an effort to protect Nadia, Milo is executed by Cheng's men. The White House attempts to cover its tracks to avoid war with Russia.

Jack seeks Buchanan's help to retrieve Josh. Phillip's men obtain Josh without living up to their end of the bargain. The situation at the White House becomes increasingly tense as Karen is arrested for covertly helping Jack, and Milo's brother reveals to Nadia just how much Milo cared for her.

Josh is rescued and Cheng is taken into custody as a war with Russia is averted. Chloe O'Brian (Mary Lynn Rajskub) and Morris discover they are going to be parents. Buchanan and Karen are both asked to retire. Jack says a final goodbye to Audrey and then stands outside looking at the ocean wondering what lies ahead for him.